In recent years, techniques for electronic apparatuses have been significantly developed, and densities and performance of integrated circuits have been rapidly increased. Accordingly, printed circuit boards have been increased in density and wiring and advanced in component surface mounting and thus required to have higher precision and performance. In order to conform to higher densities and higher performance of integrated circuits, increases in performance of solder resists used as main materials of integrated circuits have been studied. However, build-up substrates having fine internal wiring have the problem of causing cracks referred to as a “popcorn phenomenon” at an interface between a solder resist and a sealing resin, and thus solder resists having higher heat resistance have been required.
Also, with increases in integration of integrated circuits, a nano-imprint method attracts attention as an ultrafine patterning method with a line width of 20 nm or less. The nano-imprint method is roughly divided into a thermal nano-imprint method and an optical nano-imprint method. The thermal nano-imprint method includes pressing a mold to a polymeric resin softened by heating to a glass transition temperature or more and then releasing the mold after cooling to transfer a microstructure to the resin on a substrate, and is thus capable of forming nano-patterns at relatively low cost and is expected to be applied to various fields. However, the thermal nano-imprint method requires the polymeric resin to be softened by heating and thus hardly uses a polymeric resin having a high glass transition temperature. Therefore, the nano-imprint method is difficult to apply to the electric/electronic field in which higher heat resistance has recently been required.
On the other hand, the optical nano-imprint method including photocuring a composition by light irradiation has no need to heat a mold material used for pattern transfer by pressing and is thus capable of imprinting at room temperature. Photocurable resins applied to optical nano-imprint include a radical polymerization type, an ion polymerization type, and a hybrid type thereof, and any one of the types of curable compositions can be used for nano-imprint applications. However, in general, radical polymerization-type photocurable compositions are widely studied because of a wide range of material selection.
When a nano-imprint material is used as a permanent film for fine processing of thin-film transistors of a liquid crystal display, a protective film of a liquid crystal color filter, a spacer, and other members of liquid crystal display devices, a cured product of the nano-imprint material is required to have high mechanical properties, transparency, light resistance, heat resistance, and the like, and particularly required to have high heat resistance. For example, epoxy(meth)acrylate resins having a biphenyl skeleton are known as materials which can produce cured products with high heat resistance (refer to, for example, Patent Literature 1), but do not have high heat resistance required in recent years.